I was quoted this week in a Washington Post GovBeat blog story about a bill in the Colorado legislature that would legalize, on a limited basis, homeowners using rain barrels to catch the water that runs off their roofs. (See below for directions on finding the story online.) What made this little issue worthy of a national news outlet like the Post? What intrigued reporter Jeff Guo was not so much that Colorado was considering a change in law, but what the ongoing ban on residential rain barrels said about how the West manages water. His story, and my quotes, focus largely on the fundamentals and the flaws of water law in the western states. And Colorado, like a few other states, has language in its Constitution that specifies a particular system of water law: prior appropriation.

The best-known feature of prior appropriation is “first in time, first in right”–the principle that gives priority to water rights based on how early they were established. This first-come, first-served principle is not only used to allocate water among would-be users, but also to regulate water use in times of shortage; thus, under what Guo called “the dibsies approach to water management,” junior users may get no water at all in times of drought, while senior users get every drop their rights allow. And because most of the big water users in the early West were farmers irrigating their crops, most of the top-priority rights in the West are agricultural–one reason why roughly 80 percent of the region’s water use is for farm and ranch irrigation. In some states, including Colorado, the percentage is even higher.

Prior appropriation is famous for favoring the oldest water uses, but there are other ways in which it tends to lock in the status quo. First, water rights are quantified based on how much is “beneficially used” for the purpose of the right, which has always encouraged users to take and apply as much water as possible; using less could diminish the quantity and value of the water right. Second, these rights are a species of property, and so long as the water remains actively in use, they last forever. Thus, prior appropriation is a system whereby the western states have allocated water to private users, under a system that recognizes perpetual rights, and affirmatively discourages conservation. And because water rights are ordinarily restricted to the particular places and uses for which they were established, any changes require state approval–a process that can be controversial, expensive, and uncertain. This backward-looking approach to water management poses serious problems in a region that is changing fast, and in many ways.

What does this have to do with rain barrels? Colorado, which has long been influential in western water law, practices a uniquely pure form of prior appropriation that scrupulously protects senior water rights. And senior water users understandably are concerned about any change in the law that might lead to a reduction in their water supplies. Enough homeowners collecting rainwater in barrels, and using it to water their gardens, could lead to less water getting to streams and aquifers that supply water to these users. Under this view, home rain barrels are basically petty theft of water that belongs to someone else–which explains why irrigators might not like them, and legislators might hesitate to legalize them. (Some might suggest that water users should be more concerned about the impacts of climate change on their future water supplies, but that is another story.)

Guo also quoted Arizona’s Robert Glennon–who is famous for a law professor, having once appeared on The Daily Show–as saying that prior appropriation is “deeply embedded in Western water law. We academics criticize it, but it’s not going anywhere.” That is certainly true, and I observed in the story that the fact that home rain barrels remain controversial in the 21st century shows “how well-entrenched that old tenacious legal system is.” The good news is that states have shown that they are sometimes willing to adjust prior appropriation to serve important policy goals; one example is that most states passed laws allowing for “instream flow” water rights that were not recognized by old-school prior appropriation. A key question is whether states will further revise their laws to improve flexibility, promote conservation, and provide for important environmental and recreational water needs. The Colorado legislation is worth watching, mostly because its fate will say something about whether states are willing to change their laws to tackle the West’s major water problems … which are far bigger than any rain barrel.

(To find the story, search “govbeat guo march 24” — the headline is “It is actually illegal in Colorado to collect the rain that falls on your home.” Sorry I was unable to provide a working link to it here!)